Process of wet spinning stereoregular polyvinyl alcohol



Nov. 13, 1962 H. J. RYNKIEWICZ ETAL 3,063,787

PROCESS OF WET SPINNING STEREOREGULAR POLYVINYL ALCOHOL Filed June 17,1960 WIND UP RPVA SOLVENT INVENTORS HENRY J. RYNKIEWICZ EUGENE W. K.SCHWARZ IRVING SKEIST WWMEOMW ATTORNEY S United States Patent 3,063,787PROCESS OF WET SPINNING STEREOREGULAR POLYVINYL ALCOHOL Henry J.Rynkiewicz, Danbury, Conn., Eugene W. K. Schwarz, Brooklyn, N.Y., andIrving Skeist, Summit, N.J., assignors to Diamond Alkali Company,Cleveland, Ohio, a corporation of Delaware Filed June 17, 1960, Ser. No.36,739 9 Claims. (CI. 1854) This invention relates to the production offilms, fibers, threads, filaments and similar articles. Moreparticularly, it relates to the production of such articles frompolyvinyl alcohol.

It is known that polyvinyl alcohol, which is soluble in water, can bespun into fibers by wet or dry spinning methods from an aqueous solutionof the resin. Such fibers, however, are characterized by theirsensitivity, to water, particularly to hot water. If dipped in water atnormal temperature, the fiber will shrink by more than 10% of itsoriginal length, and if the temperature of the water is around 70-90 C.,the fiber will dissolve.

Polyvinyl alcohol (PVA) fibers have been made resistant to water byvarious methods including modification of the alcohol prior to spinningand by after-treatment of the fiber. It has been known to incorporateinto the polyvinyl alcohol spinning solution a compound such as adicarboxylic acid which is capable of forming a crosslinked structureunder the influence of heat. It has also been known to acetalize thepolyvinyl alcohol, then form a fiber and follow up with a heat treatmentof the fiber.

Fibers, after being spun from a PVA solution, have been made resistantto water by various treatments such as stretching and heat-treating,stretching and reacting with a material such as an aldehyde, ketone ordibasic acid, exposure to formaldehyde vapors or elevated temperaturesand treatment of the fiber surface with waxes, etc. Such treatments areexpensive and often introduce undesirable physical characteristics andimpurities in the treated fibers.

As with other types of synthetic fibers, a moderate amount of drawing orstretching orients the molecular structure and results in high tensilestrength. This orientational drawing, however, is distinguished from thestretching which accompanies the aforementioned insolubilizingtreatments.

3,063,787 Patented Nov. 13, 1962 This invention has as an object anoriented high-tensity polyvinyl alcohol fiber which, without thewell-known insolubilizing treatments, is insoluble in boiling Water. Afurther object is a method of preparing such fibers from polyvinylalcohol resins which are substantially insoluble in boiling Water. Otherobjects will be obvious from a careful study of the followingdescription of this invention.

Conventional polyvinyl alcohol is obtained by saponification, hydrolysisor alcoholysis of polymerized vinyl esters, especially vinyl acetate.The molecular weight of the polyvinyl alcohol is dependent upon that ofthe ester, i.e., a high molecular weight polyvinyl alcohol is obtainablefrom an ester having a correspondingly high molecular weight. Theconventional polyvinyl alcohol having a reduced viscosity of 1.0 iscompletely soluble in water at a temperature of about C. Accordingly, anaqueous solution of polyvinyl alcohol may be employed to produce fibers,films, etc. therefrom. v

The polyvinyl alcohol of this invention, hereafter referred to asStereoregular polyvinyl alcohol or RPVA, is obtained by alcoholysis ofpolymerized vinyl halo esters, especially vinyl chloroacetates and vinylfluoroacetates, as disclosed in US. patent application Ser. No. 689,768,filed October 14, 1957, and now Patent No. 2,901,341. The Stereoregularpolyvinyl alcohol having a reduced viscosity of 1.1 will not dissolve inwater at a temperature of 100 C. RPVA may be dissolved in water at atemperature of 1l5-120 C. The insolubility of Stereoregular polyvinylalcohol in water at 100 C. has been attributed to the syndiotacticity ofthe alcohol as contrasted to an atactic structure possessed byconventional polyvinyl alcohol.

Since pressurized equipment is necessary to maintain a water temperaturein the neighborhood of 120 C., it may be desirable to employ an organicsolvent to form the spinning solution. Stereoregular polyvinyl alcoholis not only insoluble in boiling water but is also insoluble in mostsolvents or combinations thereof. In order to determine the effect ofvarious solvents on RPVA, a film of the material was cast from a waterdispersion of the resin. The dispersion was spread on a glass plate andthe water evaporated therefrom to form a film. Small sections of thisfilm were immersed in the solvents tested and the effect of numeroussolvents is shown in Table I.

TABLE I Reagent After 5 hrs. at room After 24 hrs. at room Additional 5hrs. at Additional 2 hrs. at

temp. temp. 5055 C. 95 0.

Water NNE.-- NE. NNE. NNE. Ethylene diamiue Dissolved DissolvedDissolved Dissolved. Acetic acid, glacial NN N NE. NN V. sl. swollen.Acetic anhydride- NNE- NN NNE}- NNE. Ammonium thiochauate (sat. sol.)-Considerable swelling Considerable swelling... Considerable swelllngConsiderable swelling. Formic acid (ea-%) do do Degradation. Lithiumbromide (60% sol.) S1 swollen do Greatly swollen. Zinc chloride (60%sol.) N do Dissolved-pink. Ethylene chloride NNE at 50 C NNE at 50 CNNE. Propylene carbonate- NNE NNE NNE. Znitropropane- NNE NNE. NNE ButyrNNE NNE- Tetrahydroiurfuryl alcohol NNE NNE NNE. Chloromaleic anhydride.NNE NNE- NNE NNE. Triethylene diamine (sat. sol.) Apparentlydissolved.-. Apparently dissolved--. Apparently dissolved. Morp holine.NNE NNE NN E V. sl. swollen. N-methyl NNE NNE Degradation v. v. sl.

swollen.

Piperdine- NNE. NNE. Swollen. Pyridine NNE- NNE- N NNE-darkened.Piperazine (sat. sol.) Appears to be dissolved- Appears to be dissolved-Appears to be dissolved. Triethanolamine NNE N N E- NN NN E.Diethaunlamine NNE... NNE NNE. Nitroethaue NNE NNE NNE Acetonitrile NNE.NNE. N-acetylmorpholine NNE NNE N NNE. 1,6-hexanedian1ine-72% Appears tobe dissolved. Appears to be dissolved. Appears to be dissolved. Appearsto be dissolved.

' See footnotes at end of table.

Reagent After 5 hrs. at room After 24 hrs. at room Additional 5 hrs. atAdditional 2 hrs. at 7 temp. temp. 50-55 C. 90-95 C.

Resorcinol (sat. sol.) Swollen Considerable swelling-.- Considerableswelling. Greatly swollen. Caprolactarn (set. sol. N N E V. sl. swollendo Do. Dimethyl sulione (sat. sol.)-. Sl. swollen Swollen Do. Dime yloxide Considerable swelling... Considerable swelling. IDo. Trioresylphosphate. NNE N NE N N E. Chloroform NNE- NNE Sanoticizer 141 NN N NE.Diaeetiu NNE NNE. Formamide Sl. swollen- Sl. swollen. Triisooetyl phosphe NE--... NNE. Bis (2-ethylhexyl) hydrogen phosphate"... NNE.-. NNE.#:Hydroxypropionitrile NE Swollen. 2(2-am1noethylamine) ethanol NNE V.sl. swollen- Appears to be dissolved. 2-pyrrolidinone NE Greatlyswollen. N-methylacetamide. S1. swollen. Propargyl alcohol--. V sl. swollen V. si. swollen. Shell curing agent T l. N E N N E. Diglyme NNE NNE. Tetramethyleno sulione NNE N N E. fl-Alanine (sat. sol.) V. s1.swollen Swollen. Glycine (sat. sol.) Swo1len--... o. Guanylurea phoshate (sat. sol.) do ..do Greatly swollen Greatly swollen. Methylannnesol.) Appears to be dissolved. Appears to be dissolved- Appears to bedissolved. Appears to be dissolved. Menthaue diamine NNE NNE NNE NNE.fl-Hydroxyethyl trimethyl ammonium- V. 51. swollen V. s1. swollen S1.swollen Swollen.

bicarbonate-4 Cyanamide (sat. sol.) Considerable swelling.-.Considerable swelling. Greatly swollen Dissolved. B-Propiolactone NNE NNE NNE Si. swollen. Urea (sat. sol.) Greatly swollen Greatly swollenGreatly swollen Disslolved (may contain go Onyx ETC-% 1 Considerableswelling-.. Considerable swelling- Considerable swelling. Considerableswelling. H01 (oone.). Dissolved Dissolved Dissolved i SwollendSOz/dimethyl fomamide, saturated.--- NE- NN E. sozftetrahydroiuran,saturated NNE. LiBr/dimethyl formarnide, saturated NNE. Greatly swollenGreatly swollen. LiBr/drmethyl sulfoxrde, saturated- NNE. Extremelyswollen Extremely swollen. LlBr/tetrahydroiuran, saturated NNE- N 2ZnClz/dimethyl iormarnide, saturated. N V. v. s1. swollen NNE.znchldlmelhyl ornde, saturated-.. Extremely swollen Partially dissolved.ZnCn/tetrahydroiuran, saturated.-. NN E Dimethyl iormamide/HaO, 4:1ratio--. Extremely swollen. Dimethyl suli'oxide/HzO, 4:1 ratio S1 D0. BO/ethylene glycol, 4:1 ratio Greatly swollen. Triton X-lOOfH O, (cone.sol.)- Extremely swollen. Diacetone alcohol NNETetrahydropyran2-inethanol-. NNE. Ethyl oarbamate NNE. Ethylene glycolSwollen. Urea/tetrahydroiuran, saturated Urea/dimethyl iormamide,saturated Sl. swollen. Urea/ethylene glycol, saturated NNE. Swollen.Urealdimethyl sulfoxide, saturated Sl. swollen Extremely swollen.Urea/Z-pyrrolidone NNE Swollen. Cyanamideltetrahydroiuran, saturated-NNE.-. Cyanamide/dimethyl formamide, saturated. NNE V. v. 51. swollen.Cyanamide/ethylene glycol saturated NN E. Swollen. Cyanamide/dimethylsulfoxide. saturated- Swollen- Considerable swelling- Considerableswelling. Triethylene diamine/tetrahydrofuran NN N N E Triethylenediamine/dimethyl formamide. NNE. S1. swollen. 'lriethylenediamine/ethylene glycol Swollen. Triethylene diamine/dimethylsulioxide... Considerable swelling. Triethylene diamine/Q-pyrrolidone NNExtremely swollen. Caprolactamltetrahydroturan. 2 Csprolaetam/dirnethylformamide. S1. swollen. Caprolaetamlethylene glycol D Piperazine(hydrate) ltetrahydrofuran Piperazine (hydrate)/dimethyl iormamide- NNE.Piperazine(hydrate)/ethylene glycol Swollen. Piperazine(hydrate)/dirnethyl suli'oxide. Dissolved. Guanylureaphosphate/tetrahydrofuran- 2 Guaniylurea phosphate/dimethyl iorma- S1.swollen.

m! e. Guanylurea phosphate/ethylene glycol- Swollen. Guanylureaphosphateldimethyl sulfoxide" Considerable swelling. Diehloroaeetioacid/glycerine NN V. s]. swollen. Dichloroacetic acidltetrahydroiuran.(z) .Diehloroecetie acid/dirnethyl iormamide S1. swollen. Diehloroaoeticaoid/dimethyl sulfoxide Considerable swelling. Extremely swollen.Extremely swollen. Formio acid/ethylene glycol- NNE N N E Considerableswelling. Triethylamine NNE NNE NNE NNE. Duponol WA/HzO Considerableswelling. Considerable swelling. Considerable swelling... Considerableswelling.

1 Alkyl (CrC dimethyl benzyl ammonium chloride-25% sol. Note-NNE =Nonoticeable efieot; v.=very; sl.=silghtly; conc.=concentrated;sat.=saturated; and sol.=solution.

From Table I it will be noted that ethylene diamine, saturated solutionof triethylene diamine, saturated solution of piperazine, 72% solutionof 1,6-hexanediamine, 30% solution of methylamine and concentratedhydrochlo'ricacid apparently dissolve the stereoregular poly- Theaqueous solutions of triethylene diamine, piperazine, herranediamine andmethylamine all are quite alkaline, having a pH in the neighborhood ofabout 12. Films of RPVA which were reciprocated from these solutionswere found to be water-soluble and this led to the belief'that suchmaterials cause a possible degradation of the alcohol, accounting forits solubility. Convinyl alcohol.

I Solvent boiled off.

up to four carbon atoms.

centrated HCl is very diflicult to handle and therefore is undesirableas a solvent. For preliminary Work, ethylene diamine was selected as thesolvent in the preparation of the spinning solution.

Typically, a solution of stereoreguiar polyvinyl alcohol in ethylenediamine is extruded by means of a gear pump through a multiholespinnerette into a coagulating bath of methanol or other lower aliphaticalcohol containing From the coagulating bath the fiber or yarn is led toa positively-driven Godet and then through air to a positively-drivenWind-up bobbin. adjusting the speeds of the various drives, the fibercan 5 be stretched or drawn in controllable amounts either in thecoagulating bath or in air between the Godet and wind-up or both. It hasbec 1 found advantageous to pro vide a heat-setting operation followingthe drawing which comprises immersing the fiber or passing it through ahot mineral oil bath at a temperature of about 120 to 180 C. Thisheat-setting operation may be accompanied by a hot-stretch operationwhereby the fiber, while hot, is stretched 4 to 8 times its originallength. The combina tion of heat and stretch not only increases theinsolubility of the fiber in hot water but also orients the fiber andincreases its tensile strength.

Fibers produced from water-insoluble stercoregular polyvinyl alcoholhaving a reduced viscosity of 1.5, in accordance with this invention,have a tenacity of at least 7.5 grams per denier. Such fibers areimportant inindustrial uses such as cords for fires, fire hoses,industrial cords and belting, and in reinforcing fibers for manyapplications.

Reference has been made to the reduced viscosity (N of polyvinylalcohol. This value is an indication of the molecular weight of thepolymer and is equal to the specific viscosity (N divided by theconcentration of polymer in the solution. The fiow timeof the polymersolution I and the flow time of the solvent t are usually measured bythe capillary method. *From these values the specific viscosity iscomputed according to the formula t t o The reduced viscosity has alogarithmic relationship to the molecular weight of the polymer and, ingeneral, the range is:

Since conventional polyvinyl alcihol is soluble in water, watergenerally is used as the solvent in determining the reduced viscosity.Reduced viscosity of RPVA cannot be determined in this manner, however,since it is insoluble in water. Accordingly, the reduced viscosity ofthe precursor, i.e., polyvinyl chloroacetates or polyvinylfluoroacetates, is determined and, as is common practice in the polymerfield, this value is assumed to be proportional to the reduced viscosityof the polyvinyl alcohol.

Denier of fibers is defined as the weight in grams of a 9,000-meterlength of thread and is determined by measuring 9 meters of thread on astandard textile skeiner. The thread is removed from the skeiner andwound into a small loop about 1 inch in diameter. The loop of thread isagitated in isopropyl alcohol to remove any oil or other material whichmay be present on the thread surface and then air dried. The weight ofthe loop in milligrams, as determined on an analytical balance, equalsthe denier of the sample.

Apparatus for determining tensile strength and ultimate strengthconsists of a triple-beam laboratory scale. To one pan of the scale isattached a #25 chain which then loops over a sprocket and hand wheelnear the level of the balance, such that turning the hand wheel addsmore chain to the pan of the balance, thus gradually adding weight tothat pan. The second pan of the balance has a drum-type fiber clampattached below it. Directly below this clamp is a second clamp mountedwith a rack and pinion which, through a hand Wheel, can raise or lowerthe clamp. In operating the apparatus, the chain and sliding weights onthe balance are set at 0. The lower clamp is raised so that the clampsare inches apart. The thread sample is clamped in the upper clamp andthen pulled through the lower clamp to a point where the balance pointerreads 0 to insure that the sample is caught between clamps. The chainhand wheel is turned at a rate so as to add about 1 gram per second tothe 6 load. At the same time the other hand wheel is turned to lower theclamp, thus keeping the balance pointer at the center mark. When thethread sample breaks, rotation of both hand wheels is stopped. At thispoint the sample is checked to ascertain whether the break occurred atthe nip of the clamps and, if such is the case, that reading isdiscarded. Using the sliding weights of the balance, the weight of thechain is balanced and the reading on the scale is the breaking point.The distance the lower clamp has moved from its original positiondetermines the ultimate stretch. The arithmetic mean of 10 breakingstrength determinations is divided by the denier of the thread to givethe grams per denier. The average of 10 ultimate stretch values,calculated as a percentage of 5 inches, gives the ultimate stretchpercent.

Tenacity in grams per denier is converted to pounds per square inch bythe formula:

wherein S=strength in pounds A=cross sectional area of the fiber insquare inches d=density of the fiber in grams per cubic centimeterg=strength or tenacity in grams per denier The density of RPVA has beendetermined as 1.30 gr./cc. Substituting this value in the above formula,the tenacity in pounds per square inch is equal to 16,000Xgrams perdenier.

In order that those skilled in the art may more completely understandthe present invention and the preferred methods by which the same may becarried into effect, the following specific examples are offered.

Example 1 A prototype laboratory spinning apparatus such as is shownschematically in the attached drawing is employed which comprises areservoir for the spinning solution which feeds two positivedisplacement metering pumps which are so interconnected and are run byvariable speed motor so as to permit the accurate metering of as littleas 3 10 cc. per minute of the spinning solution. This apparatus isdesigned as a precision meter to extrude a uniform filament of spinningsolution through the spinnerette orifice. A candle filter, using muslinas the filtering medium, is mounted in such a Way as to permit thespinnerette to be raised from and lowered into the coagulating bathwithout interfering with the flow of spinning solution. The main purposeof the filter is to minimize the incidence of clogging of thespinnerette orifice. The spinnerette is attached to the filter through aglass tube. The coagulating bath is contained in a stainless steel tray,24 inches long, with an effective fiber immersion length of 18 inches.Single-stretching of the fiber is eifected by wrapping the fiber oncearound a step on a step cone, then to a rewind spool. The diameters ofthe steps are calculated to permit any elongation from 0 to 1000% in 50%increments. Sequential stretching is effected by two step cones mountedparallel and rotating at the same speed. The fiber is fed around the twosmallest diameter steps, then around successive larger steps and isfinally wound on a rewind spool. The diameters of the steps vary from Aainch to 4 inches and As-inch increments, permitting up to 700% stretchby this method.

An ethylene diamine solution containing 24% steroregular polyvinylalcohol having a reduced viscosity of about 0.4 is extruded through thespinnerette at a rate of 1.5 feet per minute into a coagulating bath ofabsolute methanol. At this extrusion rate the coagulation time is 60seconds. The fiber is subjected to a total stretch or elongation of 450%and is then dried at C. for a period of 16 hours in order to remove allof the ethylene diamine. The fiber thus produced is insoluble in boilingwater.

Example 2 A quantity of stereoregularpolyvinyl alcohol resin having areduced viscosity of 1.5 is dissolved in ethylene diamine to provide asolution of about 10% solids. Using the apparatus of Example 1, thissolution, at room temperature, is extruded through an eight-holespinnerette at a rate of 1.5 feet per minute into a coagulating bath ofabsolute methanol. The RPVA fiber is stretched a total of eight times intwo stages at ambient temperature, pressure and humidity. After drawing,the fiber is given a heat-setting treatment by immersion in a mineraloil bath at 130 to 160 C. for a period of 30 seconds. The fiber thusproduced is an eight-filament yarn of which each filament is slightlyless than one denier. This fiber is in soluble in boiling water.

Water resistance and dry tenacity of various fibers are presented inTable II:

A 10% solution of stereoregular polyvinyl alcohol in ethylene diamine ismade by placing 140 grams of anhydrous ethylene diamine in a wide-mouthglass jar. To this is added a quantity of 15.5 grams of RPVA having areduced viscosity of 1.5. The mixture is shaken vigorously to form athin slurry and then is heated for 3 hours in a water bath at 5560 C.The solution is spun through a spinnerette containing 8 orifices, eachof which is 0.003 inch in diameter, into an absolute methanol bath at aspeed which permits approximately 45 seconds coagulation bath exposure.The strand is wet-stretched 1.5 times and wound on a supply spool. Thesupply spool is placed on a hot-stretch machine where the strand ispassed through a bath of mineral oil maintained at a temperature ofabout 135-140" C. The exposure time of the strand in the bath is about20 seconds. The amount of stretch applied to the strand is varied bychanging the gear ratio of either the feed or take-01f capstan wheels sothat the speed of the take-E wheel is 3 to 10 times that of the feedwheel. Table III gives the properties of the fibers thus produced.

TABLE III Ulti- Tensile strength Denier mate (grams) Grams Pounds Hot (8filastretch per per sq. stretch ments) (perdenier in.

cent) Range Average Example 4 In order to determine the elfect ofhot-stretch bath temperature, a 10% solution of RPVA in ethylene diamineis spun into fibers as in Example 3, except that the amount ofhot-stretch is maintained at 8 times the original length and the bathtemperature is varied. Results of this test are set forth in Table IV.

Example 5 In order to determine the eifect of size or denier perfilament on physical properties, a 10% solution of RPVA in ethylenediamine is spun into filbers as in Example 3. Variation in denier iseffected by changing the speed of the solution feed pump and theresultant drawdown at the spinnerette orifices. Results are set forth inTable V.

TABLE V Strength (grams) Thread Fila- Grams Pounds Ultimate denier mentper per elongation denier Range Averdenier sq. in. (percent) age Example6 In order to determine the effect of varying both the hot-stretch bathtemperature and monofilament size, a 10% solution of RPVA in ethylenediamine is spun into fibers as in Example 3, except that the solution isspun through a 16 orifice spinnerette. The amount of hotstretch ismaintained at 8 times the original length.

TABLE VI Denier Hot stretch Tensile Grams Pounds temperastrength per per16 filament Monofilature, 0. (grams) denier sq. in

ment

It is to be understood that although the invention has been describedwith specific reference to particular embodiments thereof, it is not tobe so limited, since changes and alterations therein may be made whichare within the full intended scope of this invention as defined by theappended claims.

What is claimed is:

1. The method of producing stereoregular polyvinyl alcohol fibers whichare insoluble in water at 100 C. and have a tenacity of at least 6.8grams per denier which comprises the steps of forming a solution ofstereoregular polyvinyl alcohol in ethylene diamine containing about 3%to 24% by weight polyvinyl alcohol, extruding the solution through aspinnerette into a coagulating bath of lower aliphatic alcoholcontaining up to 4 carbon atoms, wet-stretching the fiber to about 1 to3 times its original length and hot-stretching the fiber about 4 to 12times its original length at a temperature of about 180 C.

2. The method of claim 1 wherein the solution contains about 10%polyvinyl alcohol.

3. The method of claim 1 wherein the polyvinyl alcohol has a reducedviscosity within the range of 0.4 to 1.5.

4. The method of claim 1 wherein the coagulating bath is absolutemethanol.

5. The method of claim 1 wherein the polyvinyl a1- cohol has a reducedviscosity of at least 1.5.

6. The method of claim 1 wherein the fiber is Wetstretched about 1.5times its original length and is hotstretched about 8 times its originallength at a temperature in the neighborhood of 130-l60 C.

7. The method of claim 1 wherein the fiber is hotstretched in a bath ofhot mineral oil.

8. The method of producing stereoregular polyvinyl alcohol fibers whichare insoluble in water at 100 C. and have a tenacity of at least 6.8grams per denier which comprises dissolving in ethylene diamine about10% by Weight of stereoregular polyvinyl alcohol which is insoluble inboiling water and has a reduced viscosity of at least 1.2, extruding thesolution through a spinnerette into a coagulating bath of loweraliphatic alcohol containing up to 4 carbon atoms, wet-stretching thefiber to about 1 to 3 times its original length and hot-stretching 10the fiber about 4 to 12 times its original length at a temperature ofabout 120180 C.

9. The method of claim 8 wherein the stereoregular polyvinyl alcohol hasa reduced viscosity of about 1.5 the fiber has a denier of 0.6 denierper filament, the hotstretch temperature is 171-175 C. and the tenacityof the fiber is 9.0 grams per denier.

References Cited in the file of this patent UNITED STATES PATENTS2,447,140 Shelton et al Aug. 17, 1948 2,517,694 Merion et al. Aug. 8,1950 2,610,359 Hatchard et al. Sept. 16, 1952 2,610,360 Cline et al.Sept. 16, 1952 2,642,333 Tomonari et al. June 16, 1953 2,715,763 MarleyAug. 23, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No, 3,063,787 November -l3- 1962 Henry J Rynkiewicz et al.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 2, lines 25 and 26 strike out and now Patent No, 2,901,341";columns 1 and 2 TABLE I under the column heading "Reagent" line 5, for"'thiochanate" read -thiocya-nate same table, same column lneading line18 for "Fiperd-ine" read Piperidine column 3 line 72 for"reciproEa-t-ed" read reprecipita'ted column 5 line 39 for al-cihol"read alcohol column 10, line 4 afterl'la5" insert a comma Signed andsealed this 24th day ofS-eptember 1963,

(SEAL) Attestz ERNEST w. SWIDER DAVID D Attesting Officer Commissionerof Patents

,1. THE METHOD OF PRODUCING STEREOREGULAR POLYVINYL ALCOHOL FIBERS WHICHARE INSOLUBLE IN WATER AT 100*C. AND HAVE A TENACITY OF AT LEAST 6.8GAMS DENIER WHICH COMPRISES THE STEPS OF FORMING A SOLUTION OFSTEREOREGULAR POLYVINYL ALCOHOL IN ETHYLENE DIMINE CONTAINING ABOUT 3%TO 24% BY WEIGHT POLYVINYL ALCOHOL, EXTRUDING THE SOLUTION THROUGH ASPINNERETTE INTO A COAGULATING BATH OF LOWER ALIPHATIC ALCOHOLCONTAINING UP TO 4 CARBON ATOMS, WET-STRETCHING THE FIBER TO ABOUT 1 TO3 TIMES ITS ORIGINAL LENGTH AND HOT-STREATCHING THE FIBER ABOUT 4 TO 12TIMES ITS ORIGINAL LENGTH AT A TEMPERATURE OF ABOUT 120*-180*C.